Fluid operated pump with opposed pistons and valve in middle

ABSTRACT

A fluid operated pump for oil wells having a pair of spaced pistons each of which acts as both an engine piston and a pump piston, interconnected by a piston rod, and having valve means between the pistons for controlling flow thereto, which has means for preventing excessive pressure loading on the rod during each reversal of the stroke of the pump.

States 1191 111] 3,84, cArthnr et al. [4 Nov. 19, 1979 [54] FLUIDOPERATED PUMP WllTl-il UPPOSED 2,629,329 2/1953 Rose et al. 417/393 p s'mmg AND VALVE RN MHDDLE 2,948,224 8/1950 Bailey et a1..... 417/3933,652,187 3/1972 Loeffler et al. 417/393 [75] inventors: Ralph F.McArthnr, Huntington Park; Melle 1F. Gem-1s Los Angeles, both of Calif.1 Primary Examiner Carlton R. Croyle Assistant Examiner-Richard E. Gluck73 Assignee: Kobe, 1m, Huntington Park, Calif. Attorney, s 0rFirmHarris, 111cm, Wallcn &

[22] Filed: Mar. 22, 11973 Tmsiey [2]] Appl. No.: 343,877 {57] ABSTRACTA fluid operated pump for oil wells having a pair of 152 us. ca 417/393,91/309, 91/329 spaced Pistons cach of which acts as both an cnginc 511111.131. F04 17/00, F04b 35/00, F11 25/02 Piston and a p p Piston,interconnected y a piston [58 Field of Search 417/393; 91/309, 329 rod,and having valvc mcans bctwccn t11c Pistons for controlling flowthereto, which has means for prevent- [56] References (Ii d ingexcessive pressure loading on the rod during each UNITED STATES PATENTSreversal of the stroke of the pump.

1,155,282 9/1915 Shaner 91/329 X 3 Claims, 6 Drawing Figures PATENTELNUV9 1914 SHEET 10? 3 FLUID OPERATED PUMP WITH OPPOSED PISTONS AND VALVE INMIDDLE BACKGROUND OF THE INVENTION lower face of the lower piston to theinlet of the pump,

all substantially simultaneously, or, alternatively, directing such highpressure power oil to the upper face of the lower piston, connecting thelower face of the lower piston to such discharge, connecting the upperface of the upper piston to such inlet, and connecting the lower face ofthe upper piston to such discharge, all substantially simultaneously.

Such pumps'are frequently set at substantial depths in wells, such as adepth of 6,000 feet or more, the power oil to operate the pump must bepumped at high pressure downwardly through power oil tubing to the pumpto operate it to discharge well fluid from the pump to form acolumn inthe well and to raise such column of well fluid to the surface.Differential pressures on the pistons and pump rod during operation canbe substantial. Such referencedpumps have the advantage that during bothup and down strokes the piston rod is under tension, and notcompression, permitting the design of longer pumps which is frequentlydesirable.

Such a pump is generally disclosed in the patents to Rose et al., US.Pat. No. 2,629,329, and Bailey et al. US. Pat. No. 2,948,224.

THIS INVENTION GENERALLY If with such a conventional pump, however, highpower oil pressure is admitted to the lower face of the upper pistonwhile such power oil pressure is applied to the upper face of the lowerpiston, or alternatively, power oil pressure is admitted to the upperface of the lower piston while such power oil pressure is applied to thelower face of the upper piston, as frequently occurs upon reversal ofthe pump stroke, the stress on the piston rod connecting the pistonswill be about double the normal maxium operating stress on the rod and,with the high-differential pressures involved in such a pump, can causea rod failure rendering the pump inoperative.

It is a primary object of this invention to provide such a pump havingvalve means which will insure that the maximum stress on the piston rodwill not at any time substantially exceed the normal maximum operatingstress on the rod. We prefer to accomplish this by valving the pump sothat column pressure replaces power oil pressure on a piston just priorto the end of each stroke and before power oil pressure replaces columnpressure on the other piston at the end of suchstroke, on both upstrokeand downstroke of the piston assembly.

LII

THE DRAWINGS FIG. I is a schematic vertical'sectional view of an oilwell pump embodying the invention, illustrating the pump during anupstroke of the piston assembly;

FIG. 2 is a detailed vertical sectional view of the valve portion ofFIG. 1, showing the piston assembly at the upper end of its travel, theengine valve sleeve not the having started up;

FIG. 3 is a view similar to FIG. 21, but showing the engine valve sleevein an intermediate position after starting p;

FIG. 4 is a schematic vertical sectional view of the pump, illustratingthe pump during a downstroke of the piston assembly;

FIG. 5 is a view similar to FIG. 2, but showing the piston rod assemblyat the lower end of its travel and the valve sleeve not then havingstarted down; and

FIG. 6 is a view similar .to FIG. 5 but showing the engine valve in anintermediate position after starting down.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, FIG. 1shows a generally conventional fluid operated pump 10 set in a wellcasing 11 on a bottom holeassembly I2 and provided with a power oiltubing 13. The bottom. hole assembly 12 divides the casing 11 into aproduction annulus l4 and a formation pressure zone 15 communicatingwith oil to be pumped from the surrounding formation, the pump 10 beingadapted to pump oil from the zone I5 substantially at formation pressureinto and upwardly through the production annulus 14 to the surface ofthe ground.

The pump 10 is supplied with power oil, through the power oil tubing 13,to operate the pump.

The pump 10 is provided with an upper pump cylinder'l7 having an upperpump piston 18 therein which is connected by a piston rod 19 with alower pump piston 20 in a lower pump cylinder 21, the pistons 18 and 20and their connecting piston rod 19 forming a piston assembly 16. Betweenthe upper and lower pump cylinders I7 and 21 is an engine valvemechanism, generally designated by the numeral 22.

The pump 10 has a power oil inlet passage 24 adapted to supply power oilat relatively high pressure, e.g., 5,000 p.s.i.g., from the power oiltubing 13 to the interior of the pump, such power oil being directed tothe lower face of the upper piston 18 on the upstroke of the pistonassembly 16 and, alternatively, to the top face of the lower piston 20on the downstroke of the piston assembly. The upper portion of the upperpump cylinder 17 above the upper pump piston 18 communicates through adischarge passage 26 and valve 27 with the production annulus 14 on theupstroke of the upper piston, and on the downstroke of the upper pistoncommunicates through a valve 28 and inlet passage 29 with the formationpressure zone 15 below the bottom hole assembly 12. The lower portion ofthe lower pump cylinder 21, below the lower pump piston 20, communicateson the downstroke of the lower pump piston through a discharge passage29a and valve 30 with the production annulus l4, and on the upstroke ofthe lower piston communicates through a valve 31 and inlet passage 32with the formation pressure zone 15. The engine valve mechanism 22controls such flow of fluid to and from the lower portion of the upperpump cylinder 17, to and from the upper portion of the lower pumpcylinder 21, and to and from the lower portion of the lower cylinder.

Referring to FIG. 2, the engine valve mechanism 22 includes a generallytubular valve sleeve 34 having an upper portion 35 and a lower portion36 of greater diameter and greater cross-sectional area than the upperportion. The upper portion 35 is provided with an annular recess 37 onits exterior, and the lower portion 36 is provided with aplurality ofcircumferentially spaced radial ports 38 communicating with an externalannular recess 39. The lower end of the lower portion 36 is providedwith an internal annular recess 40 which communicates throughcircumferentially spaced radial ports 41 with an external annular recess42. The piston rod 19 is provided with an upper annular recess 43 andtwo lower annular recesses 44 and 45.

The body of the pump 10, above the valve sleeve 34, is provided with anannular recess 46 around the piston rod 19 which communicates'through apassage 47 with the power oil inlet passage 24, so that at all timespower oil pressure is applied to the upper end of the upper portion 35of the valve sleeve. The recess 46 also communicates through a radialport 47a with a longitudinal passage 50, which in turn communicates withthe lower end of the upper pump cylinder 17. Below the passage 47, thebody of the pump is provided with an internal annular recess 48 whichcommunicates through a plurality of circumferentially spaced ports 49with the production annulus 14. The internal annular recess 48 alsocommunicates at its upper end with a longitudinally drilled passage 51which communicates at its lower end through radial ports 52 with anannular recess 53. The annular recess 48 communicates through radialports 54 with a longitudinal passage 55 which'in turn communicates withthe upper end of the lower pump cylinder 21 above the lower pump piston20.

FIG. 1 shows the piston assembly 16 about midway in its upstroke, andshows the valve sleeve 34 in its lowest position. At such stage in theoperation, power oil is conducted through the power oil inlet passage 24to the lower end of the upper pump cylinder 17 below the upper pumppiston 18 to exert power oil pressure on the effective area of the lowerface of the piston, such power oil pressure being referred hereinafteras P Substantially lower exhaust pressure of the production annulus 14is in the upper end of the upper pump cylinder l7 and bearing upon theeffective area of the upper end of the upper pump piston. At the sametime, the I upper end of the lower pump cylinder 21 is in directcommunication with the production annulus 14 through the longitudinalpassage 55, the ports 54, the annular recess 48, and the radial ports49, to exert the pressure (P of the fluid in the production annulus 14against the upper face of the lower pump piston 20. At the same time,the lower face of the lower piston 20 is in communication through thevalve 31, and the inlet passage 32 with the formation pressure zone 15below the pump in the well, at formation pressure, P The net upwardforce on thepiston assembly causes it to move upwardly and dischargesfluid from the upper end of both the upper pump cylinder 17 and upperend of the lower pump cylinder 21 into the production discharge annulusl4 and upwardly therethrough to the surface of the ground. During suchupward movement of the piston rod assembly power oil pressure, P isapplied to the upper endof the valve sleeve 34 and discharge pressure, Pis applied to the lower end of the valve sleeve, to retain the valvesleeve in its lowermost position during the major part of the upstrokeof the piston assembly 16.

FIG. 2 illustrates the piston assembly 16 at the upper end of itsupstroke, at which time the valve sleeve 34 has not yet started anyupward movement. In this position of the piston assembly 16, power oilpressure P, is communicated through the power oil inlet passage 24, thepassage 47, the annular recess 46, downwardly through the annularpassage formed between the interior of the valve sleeve 34 and theexterior of the piston rod 19, the recesses 44 and 45 on the piston rod,and through the annular recess 40, radial ports 41, and annular recess42 to the lower end of the valve sleeve 34. Since the lower end of thevalve sleeve 34 has a greater effective area than the upper end thereof,the valve sleeve then starts to move upwardly.

FIG. 3 shows the valve sleeve 34 after it has started to move upwardlyfrom the position shown in FIG. 2. At this point in its movement, theupper end of the valve sleeve 34 has closed off communication betweenthe radial port 47a and passage 50, leading to the lower end of theupper pump cylinder 17, and the annular recess 46 and power oil passage47. After the upward movement of the valve sleeve 34 has closed suchcommunication, further upward movement of the valve sleeve openscommunication between the lower end of the upper pump cylinder 17 andexhaust pressure P through the passage 50, the annular recess 37 andrecess 48, the passage 51, and the ports 49.

As shown in FIG. 3, the upward movement of the valve sleeve 34 has alsoopened communication between the upper end of the lower pump piston 20and power oil pressure P, through the passage 47, the annulus betweenthe valve sleeve and the outer surface of the piston rod 19, the ports54 and the longitudinal passage 55. However, just before the valvesleeve 34 reaches the position shown in FIG. 3 the recess 37 thereonwill have opened communication with the passage 50 before the recess 39opens communication through the radial ports 54 with the longitudinalpassage 55. This permits the power oil pressure P, in the lower end ofthe upper cylinder 17 to drop to discharge pressure P before thepressure P, is admitted to the upper end of the lower cylinder 21. Thus,momentarily, the pressures in the lower end of the upper cylinder 17 andthe upper end of the lower cylinder 21 are equalized, at pressure PContinued upward movement of the valve sleeve 34 to the position shownin FIG. 3 admits power oil pressure P, to the upper end of the lowercylinder 21, but only after the pressure in the lower end of the uppercylinder has been reduced to discharge pressure P The opening of theports is done by means of a passage 56 in the valve sleeve 34. As soonas this occurs, the piston assembly 16 moves downwardly on itsdownstroke, as illustrated in FIG. 4. The valve sleeve 34 then continuesits upward movement to the upper end of its stroke, shown in FIGS. 4 and5.

During the downstroke of the piston assembly 16, illustrated in FIG. 4,the valve sleeve 34 remains in its uppermost position illustrated inFIGS 4 and 5. It is to be noted that in FIGS. 1 and 4 the valve sleeve34 is shown diagrammatically in side elevation and that, to understandthe detailed construction of t the valve sleeve and its porting,reference must be made to the other detailed figures showing the same.

Upon completion of the downstroke of the piston assembly 16, shown inFIGS. 5 and s, the valve sleeve 34 starts to move downwardly from itsuppermost postion shown in FIGS. 4 and 5, due to the fact that power oilpressure P bears on the small upper end of the valve sleeve whereas thelower larger end of the valve sleeve is connected to discharge pressureP as shown in FIG. 5. Such pressure differential causes the downwardmovement of the valve sleeve 34. During such downward movement of thevalve sleeve 34 the recess 37 passes out of communication with the port47a and the longitudinal passage 50 to close off communication betweenthe lower end of the upper cylinder 17 and discharge pressure P and alsoopens communication between the upper end of the lower pump cylinder 21and discharge pressure P both as illustrated in FIG. ti. Continueddownward movement of the valve sleeve 34 causes its upper end 35 toclear the port 47a leading to the longitudinal passage 50, as shown inFIG. 2, to admit power oil pressure P, from the recess 46 through thelongitudinal passage 50 to the lower end of the upper pump cylinder 17,to start the upstroke of the piston assembly 16. At the start of theupstroke of the piston assembly 16 it is in the position shown in FIG.6, with the valve sleeve 34 a bit farther down than as shown in FIG. 6,to admit power oil to the passage 50 as illustrated in FIG. 1. Thus, atthe conclusion of the downstroke of the piston assembly 16 the pressureson the upper end of the lower pump piston 20 and the lower end of theupper pump piston 18 are equalized at discharge pressure P before poweroil pressure P is admitted to the lower end of the upper pump piston tostart the upstroke. Thus, at no time during the operation of the pump isthe piston rod 19 under any greater tension than it is during the normalstrokes of the piston assembly 16, which is an important object of theinvention.

We claim:

I. In a fluid operated pump, the combination of:

an elongated pump assembly having a main body including an upper pumpingcylinder having an upper pump piston therein and a lower pumpingcylinder below said upper cylinder and having a lower pump pistontherein, said pistons being rigidly connected together by a piston rodtherebetween, said pump having power fluid inlet passage means adaptedto be connected to a source of power oil under high pressure, havingwell fluid inlet passage means adapted to be connected to a source ofwell fluid at substantially lower pressure, and having discharge passagemeans adapted to receive fluid pumped by the pump and discharge it intoa conduit leading to the surface of the ground, the fluid pressure insaid discharge passage means being intermediate between the fluidpressures in said power fluid inlet passage and said well fluid inletpassage; and

valve means in said pump adapted to connect said power fluid inletpassage means to the lower end of said upper cylinder below said upperpiston, said well fluid inlet passage means to the lower end of saidlower cylinder below said lower piston, and said discharge passage meansto the upper ends of said cylinders above the pistons therein to causean upstroke of the pump, and alternatively adapted to connect said powerfluid inlet passage means to the upper end of said lower cylinder abovethe piston therein, said well fluid inlet passage means to the upper endof said upper cylinder above said piston therein, and said dischargepassage means to the lower ends of said cylinders below the pistonstherein to cause a downstroke of the pump, said valve means on theupstroke of the pump connecting said discharge passage means to thelower end of said upper cylinder before it connects said power fluidinlet passage means to the upper end of said lower cylinder, said valvemeans on the downstroke of the pump connecting said discharge passagemeans to the upper end of said lower cylinder before it connects saidpower fluid inlet passage means to the lower end of said upper cylinder,said valve means including a tubular valve sleeve encircling said pistonrod and longitudinally movable relative to the main body of said pump inresponse to differential fluid pressures applied thereto.

2. A pump as defined in claim I in which said valve sleeve has a firstend constantly in communication with said power fluid inlet passagemeans, and has a second end of larger effective cross-sectional areathan that of said first end and which is alternatively in communicationwith said power fluid inlet passage or said discharge passage means.

3. A pump as defined in claim 3 in which said piston rod has meanscontrolling the application of fluid pressures to said valve sleeve.

{3 3 UNITED STATES PATENT OFFICE CERTIFICATE-OF CORRECTION Patent No.3,849,030 "f D u vemberlxmm.

Invencms) 11 F. 'MgiArthu r and "Melle Geurts It isrcerti fied that error appears in the aboveridentif ied 'pt'e nt i and that said LettersPatent are hereby corrected as shown belowi si ned a d seal t i'sll'thday ofFe'brilary 197$;

(SEAL) Attest-z I l c. MARSHALL DANN Y RUTH C. MASON Commissioner pfPatents wy,

Attesting Offi'cer s andTrademarks

1. In a fluid operated pump, the combination of: an elongated pumpassembly having a main body including an upper pumping cylinder havingan upper pump piston therein and a lower pumping cylinder below saidupper cylinder and having a lower pump piston therein, said pistonsbeing rigidly connected together by a piston rod therebetween, said pumphaving power fluid inlet passage means adapted to be connected to asource of power oil under high pressure, having well fluid inlet passagemeans adapted to be connected to a source of well fluid at substantiallylower pressure, and having discharge passage means adapted to receivefluid pumped by the pump and discharge it into a conduit leading to thesurface of the ground, the fluid pressure in said discharge passagemeans being intermediate between the fluid pressures in said power fluidinlet passage and said well fluid inlet passage; and valve means in saidpump adapted to connect said power fluid inlet passage means to thelower end of said upper cylinder below said upper piston, said wellfluid inlet passage means to the lower end of said lower cylinder belowsaid lower piston, and said discharge passage means to the upper ends ofsaid cylinders above the pistons therein to cause an upstroke of thepump, and alternatively adapted to connect said power fluid inletpassage means to the upper end of said lower cylinder above the pistontherein, said well fluid inlet passage means to the upper end of saidupper cylinder above said piston therein, and said discharge passagemeans to the lower ends of said cylinders below the pistons therein tocause a downstroke of the pump, said valve means on the upstroke of thepump connecting said discharge passage means to the lower end of saidupper cylinder before it connects said power fluid inlet passage meansto the upper end of said lower cylinder, said valve means on thedownstroke of the pump connecting said discharge passage means to theupper end of said lower cylinder before it connects said power fluidinlet passage means to the lower end of said upper cylinder, said valvemeans including a tubular valve sleeve encircling said piston rod andlongitudinally movable relative to the main body of said pump inresponse to differential fluid pressures applied thereto.
 2. A pump asdefined in claim 1 in which said valve sleeve has a first end constantlyin communication with said power fluid inlet passage means, and has asecond end of larger effective cross-sectional area than that of saidfirst end and which is alternatively in communication with said powerfluid inlet passage or said discharge passage means.
 3. A pump asdefined in claim 3 in which said piston rod has means controlling theapplication of fluid pressures to said valve sleeve.